The subject invention relates generally to systems for preventing removal or relative motion between parts, to methods and apparatus for operating magnetic locking assemblies, to magnetic locks and similar fastening devices, and to monitoring and tampering detection systems for magnetic locking assemblies and similar structure.
For a magnetic lock to be locked, two criteria must be met. First, the lock must be energized or magnetized at or near full power, such that the requisite holding magnetic field is present. Secondly, the lock must be properly mated to its strike plate, with no appreciable amount of debris or air gap between the face of the lock and the strike plate. If, and only if, these two conditions are met, the magnetic lock may be said to be "locked"; that is, to be holding at full force. In practice, these criteria apply generally to various devices and apparatus employing a magnetic locking assembly, including not only locks, but also such devices as magnetic fasteners, mounting structures, lifters, couplings, theft prevention contrivances, and the like.
Existing magnetic locking systems have fallen short of meeting the above criteria in a reliable and reasonably tamperproof manner. For instance, existing magnetic locks employ such proximity sensors as electric switches actuated by the strike plate or magnetic reed switches actuated by a permanent magnet located in or at the strike plate of the lock. Such arrangements, however, at best are only capable of detecting the presence of the strike plate at the lock, while remaining incapable of ascertaining whether the electromagnetic lock is energized and holding at full force. In consequence, existing systems of the type under consideration will provide a deceptive "all is well" indication when the magnetic lock has not even been energized.
As another drawback, existing proximity sensors and other supposed safety features are easily defeated by external magnetic fields or other force-producing contrivances.
In a similar vein, it is a well-known practice of intruders and saboteurs to defeat or impair the operation of magnetic locking devices by an artificial provision of debilitating air gaps or other artifacts which weaken the holding power of the locking assembly upon energization thereof. For instance, even a thin tape applied to the pole face of a magnetic lock during its open condition, will render it relatively easy for an intruder to push open a supposedly securely locked assembly. No effective methods for precluding such tampering and intrusions have heretofore been known.
It is a general object of this invention to overcome the disadvantages and meet the needs expressed or implicit in the above statement or in other parts hereof.
It is a germane object of this invention to provide improved magnetic locking assemblies in a broad sense, including electromagnetic locks, magnetic theft prevention systems, magnetic fasteners, mounting devices and similar apparatus.
It is a related object of this invention to provide reliable status detection, verification and indication systems for magnetic locks.
It is a related object of this invention to detect or identify locking power diminutions between components of magnetic locking assemblies.
It is a germane object of this invention selectively to provide alarm conditions in response to locking power diminutions.
It is also an object of this invention to detect or identify instances of tampering with magnetic locks and attempts at defeating their effective operation.
Other objects will become apparent in the further course of this disclosure.